1. Field of the Invention
The present invention relates to a display device. More particularly, the present invention relates to a video muting device of a display device, for preventing transient phenomena generated when changing an operation mode, and a muting method thereof.
2. Description of the Related Art
General display devices such as monitors include video muting devices to prevent transient phenomena and noise from being displayed on a screen, with the transient phenomena or noise being generated while operation modes are being changed, for example, when turning on/off the power, changing sub-modes, and entering a dynamic power management (DPM) mode.
FIG. 1 shows a schematic block diagram of the video muting device provided in a conventional display device. As shown in FIG. 1, the video muting device includes a scaler 10 for converting an input signal into a predetermined resolution, and a control part 30 for determining whether a mode of the display is changed and generating a mute signal. The control part 30 determines the mode change according to a type of signal input to the display device.
An analog video signal, including a red-green-blue (RGB) signal, and horizontal-synchronization (H-sync) and vertical-synchronization (V-sync) signals is input to the scaler 10. The RGB signal input to the scaler 10 is processed by an analog-digital converter (ADC), a phase lock loop (PLL), scaled, based on the H-sync and V-sync signals, and output. The H-sync and V-sync signals are input to the control part 30, and the control part 30 determines the resolution and change of modes based on the H-sync and V-sync signals. More specifically, when any of the H-sync and V-sync signals do not exist, the control part 30 determines the changed mode of the display and generates a mute signal.
A digital video signal which has the RGB signal and a clock (CLK) signal is input to the scaler 10. The scaler 10 counts the CLK signal to calculate horizontal-total (H-total) and vertical-total (V-total) and store them to a predetermined register. The control part 30 determines the resolution and change of modes based on the H-total and V-total stored to the register. In other words, the control part 30 reads the register value and compares the value with a table of the H-total and V-total according to different modes, as well as applicable resolution conversions, provided in the control part 30, thereby determining the modes and a change of modes. When the register value is changed, the control part 30 identifies the mode as having been changed and generates the mute signal.
As can be appreciated from the above description, in the conventional case, the analog signal, the H-sync and V-sync signals are directly input to the control part 30 to determine whether the mode has changed. However, when a digital signal is input, the scaler 10 first counts the CLK to obtain the H-total and V-total, and then the control part 30 reads and compares the H-total and V-total so as to determine whether the mode has changed. Accordingly, a mode change determination takes longer with the digital signal, compared to the analog signal.
Thus, in a conventional muting system for a digital signal, as described above, the control part 30 identifies a change in the H-total and V-total from the moment that they are changed. Therefore, during the time when the H-total and V-total change, until when the control part identifies the change and generates the mute signal, the transient phenomena and noise can not be removed.